IfADo-Leibniz Research Centre for Working Environment and Human Factors, Ardeystraße 67, 44139 Dortmund, Germany.
J Neurophysiol. 2013 Jun;109(11):2680-90. doi: 10.1152/jn.01101.2012. Epub 2013 Mar 13.
Extending the body with a tool could imply that characteristics of hand movements become characteristics of the movement of the effective part of the tool. Recent research suggests that such distal shifts are subject to boundary conditions. Here we propose the existence of three constraints: a strategy constraint, a constraint of movement characteristics, and a constraint of mode of control. We investigate their validity for the curvature of transverse movements aimed at a target while using a sliding first-order lever. Participants moved the tip of the effort arm of a real or virtual lever to control a cursor representing movements of the tip of the load arm of the lever on a monitor. With this tool, straight transverse hand movements are associated with concave curvature of the path of the tip of the tool. With terminal visual feedback and when targets were presented for the hand, hand paths were slightly concave in the absence of the dynamic transformation of the tool and slightly convex in its presence. When targets were presented for the tip of the lever, both the concave and convex curvatures of the hand paths became stronger. Finally, with continuous visual feedback of the tip of the lever, curvature of hand paths became convex and concave curvature of the paths of the tip of the lever was reduced. In addition, the effect of the dynamic transformation on curvature was attenuated. These findings support the notion that distal shifts are subject to at least the three proposed constraints.
用工具延伸身体可能意味着手部运动的特征成为工具有效部分运动的特征。最近的研究表明，这种远距离转移受到边界条件的限制。在这里，我们提出存在三个约束条件：策略约束、运动特征约束和控制模式约束。我们研究了它们在使用滑动一阶杠杆进行横向运动时对曲率的有效性，目标是瞄准目标。参与者移动力臂的末端来控制光标，光标代表杠杆的负载臂的末端的运动。使用这种工具，直接的横向手部运动与工具末端的路径的凹曲率相关联。在手存在视觉反馈和目标呈现的情况下，在手不存在工具的动态变换时，手路径略呈凹形，在手存在工具的动态变换时，手路径略呈凸形。当目标呈现给杠杆的末端时，手路径的凹曲率和凸曲率都变得更强。最后，在手末端的连续视觉反馈下，手路径的曲率变得凸形，杠杆末端的路径的凹曲率减小。此外，动态变换对曲率的影响减弱。这些发现支持这样一种观点，即远距离转移至少受到三个建议的约束条件的限制。
